a. A flux of 0.2 × 10−4 Wb will establish sufficient attractive force for the armature of...

a. A flux of 0.2 × 10−4 Wb will establish sufficient attractive force for the armature of the relay in Fig. 1 to close the contacts. Determine the required current to establish this flux level if we assume that the total mmf drop is across the air gap.

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b. The force exerted on the armature is determined by the equation

 

where Bg is the flux density within the air gap and A is the common area of the air gap. Find the force in new- tons exerted when the flux Φ specified in part (a) is established.

FIG. 1

Relay.